The standard 4-band 20 ohm resistor color code is Red, Black, Black, Gold (indicating 20Ω with a 5% tolerance). For a precision 5-band 1% resistor, the code is Red, Black, Black, Gold, Brown. In surface-mount (SMD) packages, a 20 ohm resistor is marked as 200 or 20R0.
Because 20 ohms is a relatively low resistance value, the multiplier band behaves differently than it does for standard kilo-ohm or mega-ohm resistors. Below is the complete reference data, standard variants, and bench-level troubleshooting for faded components.
The 20 Ohm Resistor Color Code Breakdown
Resistor color codes follow a strict digit-multiplier-tolerance sequence. For a 20 ohm value, the significant digits are always 2 and 0, but the multiplier shifts depending on whether you are reading a 4-band or 5-band component.
| Package / Type | Band 1 | Band 2 | Band 3 | Band 4 (Multiplier) | Band 5 (Tolerance) | Result |
|---|---|---|---|---|---|---|
| 4-Band Axial (5%) | Red (2) | Black (0) | Black (×1) | Gold (±5%) | N/A | 20Ω ±5% |
| 5-Band Axial (1%) | Red (2) | Black (0) | Black (0) | Gold (×0.1) | Brown (±1%) | 20.0Ω ±1% |
| 5-Band Axial (2%) | Red (2) | Black (0) | Black (0) | Gold (×0.1) | Red (±2%) | 20.0Ω ±2% |
| SMD (0805 / 1206) | Printed Code: 200 (20 × 10^0) or 20R0 | 20Ω ±1% or 5% | ||||
Core Color Reference Data
To decode any resistor on your bench, you need the master IEC 60062 color chart. Here are the specific values relevant to low-ohm decoding:
| Color | Digit Value (Bands 1-3) | Multiplier Value (Band 3 or 4) | Tolerance (Final Band) |
|---|---|---|---|
| Black | 0 | ×1 (10^0) | — |
| Brown | 1 | ×10 (10^1) | ±1% (F) |
| Red | 2 | ×100 (10^2) | ±2% (G) |
| Gold | — (Not a digit) | ×0.1 (10^-1) | ±5% (J) |
| Silver | — (Not a digit) | ×0.01 (10^-2) | ±10% (K) |
Standard Variants: IEC 60062 vs. Legacy Specs
While the color bands themselves are universal, the governing standards and schematic notations differ by region and era. Knowing which standard applies prevents misinterpretation when reading older schematics or sourcing military-grade surplus.
IEC 60062 (Global Standard)
The International Electrotechnical Commission (IEC) standard 60062 is the current global authority for resistor color codes and SMD markings. It dictates the exact RGB values for the paint bands and standardizes the 'R' notation for SMD and schematic decimals (e.g., 20R instead of 20.0). If you are buying components from Mouser, Digi-Key, or standard Asian manufacturers today, they adhere to IEC 60062.
Legacy BS1852 (Old UK Standard)
Before harmonization with Europe, the UK used British Standard BS1852. While the physical color bands were identical to the modern standard, BS1852 formalized the 'R' decimal placeholder in printed schematics and component printing to avoid the 'decimal point invisibility' problem on old photocopies. You will still see '20R' printed on older UK-designed PCBs (like vintage Marshall amplifiers or early Sinclair electronics). BS1852 was officially withdrawn and replaced by BS EN 60062, but the 'R' notation survived and was absorbed into the modern IEC standard.
MIL-PRF-22684 / MIL-SPEC (US Military)
US military-specification resistors often use a 5-band system where the final band does not indicate tolerance. Instead, the 5th band indicates the reliability level (failure rate per 1,000 hours), while the 4th band indicates tolerance.
Warning: If you are salvaging MIL-SPEC gear, a 5-band resistor reading Red-Black-Black-Gold-Brown might not be a 1% tolerance part. In the MIL-SPEC system, if the 4th band is Gold (±5%) and the 5th band is Brown (1% failure rate), it is a 20Ω ±5% resistor with a 1.0% reliability rating. Always cross-reference the manufacturer's CAGE code and MIL-SPEC datasheet before trusting the 5th band as a tolerance marker on military boards.
Rows People Get Wrong & Faded Marking Protocols
Low-ohm resistors like the 20Ω value introduce specific reading errors that do not occur with standard 10kΩ or 100kΩ resistors. Here is how to avoid the most common bench mistakes.
The Multiplier Trap: Gold vs. Black
The most frequent error when reading a 5-band 20 ohm resistor is misidentifying the Gold multiplier band as the tolerance band.
In a standard 5-band 10kΩ resistor, the bands are Brown-Black-Black-Red-Brown. The 4th band (Red) is a whole-number multiplier.
But for 20.0Ω, the math requires multiplying 200 by 0.1 to get 20. Therefore, the 4th band must be Gold. Many hobbyists see Gold, assume it is the 5% tolerance band, and read the resistor backward or assume it is a 4-band component. Rule of thumb: If a 5-band resistor has a Gold band in the 4th position, it is a sub-100 ohm precision resistor.
Red vs. Brown Degradation
Under fluorescent bench lighting or when a resistor has been subjected to heat, the Red band (Digit 2) and the Brown band (Digit 1 or Tolerance) can look nearly identical. If you suspect a 20 ohm resistor (Red-Black-Black) is actually a 10 ohm resistor (Brown-Black-Black), do not rely on visual inspection. Heat stress shifts the red pigment toward a muddy brown.
Safe Interpretation of Faded or Burnt Markings
If a 20 ohm resistor has overheated, the epoxy coating may blister, and the color bands will char or fade entirely. To safely interpret the value:
- Desolder one leg: Never measure a low-value resistor in-circuit. Parallel circuit paths will almost always yield a false low reading.
- Zero your test leads: Standard multimeter test leads have an inherent resistance of 0.2Ω to 0.5Ω. When measuring a 20Ω resistor, a 0.4Ω lead resistance introduces a 2% measurement error before you even touch the component.
- Use REL (Relative) Mode: Short your probes together and press the 'REL' or 'NULL' button on your DMM (like a Fluke 87V or Brymen BM235) to subtract the lead resistance.
- 4-Wire Kelvin Measurement: For 1% or 0.1% precision 20 ohm shunt resistors, use a bench DMM with 4-wire Kelvin clips to eliminate lead resistance entirely.
For comprehensive testing procedures and multimeter calibration standards, refer to the Fluke guide on resistance measurement. Always verify your DMM's accuracy on a known precision calibration resistor before trusting it to diagnose faded 20 ohm components in high-current sensing applications.
